1. Field of the Invention
The present invention relates to the production of alcohol and, more particularly, to a unique and improved apparatus for producing ethyl alcohol from cereal grains and like materials.
2. Description of the Prior Art
As is known in the art, commercial processes or techniques for producing ethyl alcohol from sugars involves the fermentation of glucose, the latter being in turn derived from starch or molasses. If molasses is employed no preparatory treatment is required. For grains such as, e.g., corn, wheat, rice, etc., it is necessary to convert the starch into glucose. In accordance with a process known as malting (converting starch to glucose), barley is steeped in water and allowed to germinate. During germination, an enzyme, diastase, is developed. The germinated barley is dried (malt) and when added to starch suspensions from grains converts the starch into maltose: ##EQU1##
Maltase, an enzyme produced by yeast, converts maltose to glucose. The glucose is decomposed to ethyl alcohol and carbon dioxide by the action of the enzyme zymase. With active yeast, the fermentation may be complete in two-three days. The alcohol is recovered from the fermentated solution by fractional distillation.
It has been stated that the fermentation of alcohol is as old as the yeast that causes it, with alcohol, in the form of wines, beer and spirits, being, for all practical purposes, prehistoric. Perhaps because of this fact, tradition still plays a large part in processes or techniques used for producing ethyl alcohol from cereal grains. This is true, notwithstanding the commercial significance of this industry. It should be apparent that modern thinking and technology should be employed where possible and it is this end to which the present invention is directed.
In this regard and again broadly speaking for the moment, conventional process steps involved in the fermentation of alcohol from cereal grains include: (1) milling of the grain; (2) mashing or cooking; (3) malting; (4) fermentation; and (5) distillation. Although various known apparatus and procedures are presently employed for carrying out each of the above steps or operations, in many instances little concern has been shown for their inherent disadvantages, nor have attempts been made, at least to the knowledge of the present inventor, to investigate certain basic concepts upon which each is based. For example, in milling, three basic types of apparatus are employed. These include the hammer mill, the attrition mill and the roller mill. All three types, however, have been found to leave portions of the grain as sharp, hard particles which results in significant time and energy (as heat) being required for the proper wetting of the grain with water to produce complete hydration.
In conventional operations the preparation of the mash (step 2) generally involves: (a) mixing the milled grain with water; (b) preparing the starch by heating or cooking; and (c) cooling. Most of the variables are to be found in the manipulation of time and temperature involved in the cooking. Three general combinations of the above principals are commonly followed. These include:
(1) Mixing the grain and water at low temperature, and step-wise elevating the temperature. Malting is done at any time in the process before the cook reaches top temperature;
(2) Mixing the grain and water at a desired temperature then raising the temperature and cooling to the malting temperature; and,
(3) Mixing the grain and water at a desired temperature, holding to liquefy the starch, and then cooking to boiling, or, under pressure, cooling to malting temperature.
When using the first method (1), malting is usually done early in the process. The process can produce undesirable hydrolytic products of starch and leave raw or unconverted starch in the mash. In method (2), the object is to heat the mash for gelling the starch and sterilization before malting. In many instances the heating is done step-wise to permit liquefying of the starch prior to the formation of the gell or reaching the boiling point. If liquefication is not effected, the mash becomes very thick, requiring much power for stirring and cooling. If liquefication is done, alteration of the starch is inherent with the liquefication, thus changing the malt substrate. The third technique (3) involves the preparation of a grain slurry which is held for a scheduled time prior to boiling or pressure cooking. This method is the most severe on the starch, presenting the greatest chance for alteration of the starch by enzymes, excessive heat and inappropriate use of time.
As previously noted, the use of malt for converting the grain starch to usable yeast food (glucose) is dependent on diastatic enzymes. These enzymes are water soluble and are extractible from the ground malt. Here, the customary practice is to mill the malt to a fine powder, suspend the powder in about two pounds of water per pound of malt, and add the slurry to the main mash. If the malt is added to an ungelled mash, the temperatures are usually low, permitting full play of the enzymes during step-wise elevation of temperature. If added to a gelled mash, the malt slurry is added at about 140.degree. F., held at that temperature for the desired time and then cooled. In all cases, it is necessary that care be taken to leave substantial amounts of diastase in the finished mash. This is necessary because in known processes not all the starch is converted before delivery to the fermenter. In the fermenter there is sufficient time for residual diastase to complete its work.
In conventional mashing process, the end product is maltose (a disacharide). This the yeast does not use directly, but has its own enzyme (maltase) which splits the maltose into two molecules of glucose. In general, the time required to hydrolyze all of the starch to sugars is too great to be economical (a process often requiring many hours). The usual practice is to make sure that a very large amount of diastase acts slowly at fermenter temperatures so as to remove all of the starch in the course of a normal fermentation. A mash from grain, however, will carry many types of organisms, which may flourish on the mash, producing undesirable by-products and acid. Excess acidity not only slows the action of the yeast but represents a significant amount of yeast food.
The stripping of the alcohol from a fermented mash or beer is a standard operation founded on the physics of boiling mixtures. This operation generally presents no problem except that the steam condensate dilutes the residue or "stillage." The residue of grain after fermentation is valuable. Any unnecessary addition of water is therefore an added expense.
While many of the above problems or concepts of traditional distilling operations are art recognized, their disadvantages remain. The present invention is directed to their solution and the application of modern technology to the art of producing ethyl alcohol from grains or like materials.